| Nitrogen, as the largest demand nutrient element for plants, is freely soluble in water. Nitrogenous fertilizer is essential in fertigation which contributes to the groundwater pollution as the major factor as well. The manuring time, quantity and spot can be flexibly applied according to the plants need in fertigation. The fertigation can ensure the nutrient supply to the plant, enhance the nitrogen use efficiency, and avoid the nutrient leaching loss. Nitrogen application rate, method and nitrogen fertilizer type are three important management elements of water and fertilizer in fertigation. The variation of these parameters can affect the crop growth, yield and residual nitrate in soil. At present, studies of the fertigation application to the field crops are very few in China. The research about the crop rotation of winter wheat and summer maize in north of China is more scarce.The experiments were conducted in Langfang experiment station of CAAS in Hebei province. Different nutrient application method, rate and different nutrient fertilizer type were designed in the fertigation field experiments.9treatments were included with three replicates. The nutrient application method treatments include conventional fertilization (with clean drip irrigation water and nutrient fertilizer spreading over the field) and fertigation (with irrigation water mixed with nutrient fertilizer).4N levels of fertigation (winter wheat,325kgN-hm·2,250kgN·hm-2,175kgN·hm-2and100kgN·hm-2; summer maize,267.15kgN·hm-2,205.5kgN·hm-2,143.85kgN·hm-2and82.2kgN·hm-2) were designed as the nutrient application quantity treatments.3different nitrogen fertilizer types (ammonium nitrate, ammonium sulfate and calcium nitrate) were applied in the experiments. The physiological and ecological indexes (plant height, leaf area index, photosynthetic rate, transpiration rate and so on) and productions of winter wheat and summer maize were measured at regular intervals. The effect of different fertigation treatments on quality, yield and nutrient absorption of crop and residual nitrate in soil is analyzed. Theoretical basis for field crop fertigaion management and technology in the north of China will be provided. Major conclusions were described as followings:1. The growths of winter wheat and summer maize were affected by different nitrogen application method, especially the winter wheat. Compared to the drip irrigation+conventional fertilization, fertigation improved the height, LAI, chlorophyll metabolism and the functional period of leaves of the winter wheat. Under the same nitrogen application, the winter wheat dry matter of fertigation in mature increase by73.3%and that of the reducing60%nitrogen treatment increase by72.5%. As for the summer maize, sifnificant difference existed between the LAI of drip irrigation+conventional fertilization and fertigation, but no significant differences was found between plant height of them. Under the same nitrogen application, the largest LAI of summer maize of the drip irrigation+conventional fertilization treatment decreased by1.83%compared to the fertigaion treatment. No differences was found between the chlorophyll content of drip irrigation+conventional fertilization and fertigation. In the grainfilling period, the photosynthetic rate of summer maize increased significantly than the fertigation treatment.2.Compared to the drip irrigation+conventional fertilization treatment, the winter wheat yield, water use efficiency and nitrogen use efficiency of fertigation treatment increased significantly, and the fertigation under same nitrogen application significantly increased the wheat yield, water use dfficiency and nitrogen use efficiency significantly, and the increasing amount of wheat yield was2137.11kg·hm-2, increasing range of wheat yield, water use dfficiency and nitrogen use efficiency were79.7%,59.1%and760%respectively. The wheat yield and water use sfficiency of the reducing60%nitrogen treatment increased significantly than the drip irrigation+conventional fertilization treatment which the increase amount was2648.76kg·hm-2and increase range of wheat yield and water use dfficiency were98.7%and88.95. In high level nitrogen rate of fertigaion, photosynthetic products of winter wheat were mainly used in vegetative formation and population growth. but in low nitrogen application, photosynthetic products of wintner wheat was mainly enhanced the ability of nitrogen uptake from soil to increase assimilation product transfer to grain sink and improve harvest index. In100kgN·hm-2application of fertigation, improving nitrogen fertilizer input ratio in tillering and reducing in the flowering and post-production period nutrient supply get the maximum yield benefit. No significant difference was found between the maize yield and water use efficiency of fertigation and drip irrigation+conventional fertilization and the different nitrogen treantment quality treatment. The fertigation treatment of82.2kgN·hm-2significantly increased the nitrogen use efficiency and tyield. Under the treatment of fertigation, reducing the nitrogen application ratio in jointing stage and increasing the application in tilling stage improved the summer maize yield. In winter wheat-summer maize rotation system, difference was found between the two crops to different irrigation and fertilization regime treatment.3. More residual nitrate was found in soil in drip irrigation+conventional fertilization than fertigation treatment. Among the4nitrogen fertigation levels, the same nitrate nitrogen distribution pattern with a descending rank order of30cm away form root>15cm away from root>0cm away from root and no obvious ammonium nitrogen distribution pattern we found between them. Low nitrogen application rate in fertigation decreased residual mineral nitrogen and reduced environmental risk4. Compared to the ammonium nitrogen+nitrate nitrogen treatment, the dry matter accumulation and nitrogen use efficiency of winter wheat were higher than only ammonium nitrogen or nitrate nitrogen treantment. The growth and development response of winter wheat to ammonium or nitrate nitrogen were related to reproductive period, before the grouting period, winter wheat may absorb nitrate nitrogen first, and after grouting period, winter wheat may absorb ammounium nitrogen first.5. The highest yield of summer maize was found in calcium nitrate fertilizer for fertigation and the maize yield in ammonium nitrate fertilizer was lowest. The growth and development response of summer maize to ammonium or nitrate nitrogen was related to reproductive age, before the grouting period, summer maize may absorb nitrate nitrogen first, and after grouting period, summer maize may absorb ammounium nitrogen first.6. same distribution pattern was found in different nitrogen form for fertigation:nitrate nitrogen was the major mineral nitrogen form in the soil, the concentration was higher in root and far away from root and lower in near from the root, no difference was found in root of the ammonium nitrogen concentration. Linear relationship existed between residuel nitrate nitrogen and yield and the correlation coefficient was0.9275. |
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